In recent years, a three-dimensional information visualizer displaying a logical three-dimensional space on a screen of a personal computer or the like, in which a user can take a walk in the logical three-dimensional space displayed on the screen by manipulating an input device such as a mouse or a keyboard, has been put to practical use. The following examples are commonly utilized: a device which three-dimensionally displays an image of a shopping mall on the screen so that the user feels as if he or she was actually shopping on the screen; and a visualizer in which images of books are three-dimensionally placed and the user can visualize the content of the book he desires to read by double-clicking the image of the book.
On the other hand, more and more users read information stored in servers located all over the world via the internet in recent years. For example, in a system called "World Wide Web" (hereinafter, referred to as "WWW"), information which is created by users on the servers (referred to as "Web pages" or simply "pages") can be retrieved and read via communication lines all over the world.
The information on pages is written in a language called Hypertext Markup Language (abbreviated as HTML), so that a special software called a browser is used for interpreting the written information so as to display the information on the screen. A well-known example of such a browser is Netscape Navigator (brand name) manufactured by Netscape Communications Corporation.
The Netscape Navigator is provided with a bookmark function. The bookmark function refers to a function by which, in the case where a user reads information on a certain Web page, the read page is registered as a bookmark, and after the user has moved to another page, the user can immediately return to a desired page by designating the registered bookmark.
The identification assigned to each of the Web pages is referred to as "Uniform Resource Locator (hereinafter, referred to as URL)", and the user can designate a desired page by designating the URL. However, the operation of inputting the URL is often troublesome.
The bookmark function realizes easy access to a page which has already been read, without performing the input of the URL every time the user desires to read the page, thus significantly improving operability of the browser.
However, the above-mentioned bookmark function simply accumulates the URLs of the pages which are registered as the bookmarks in the order of the registration. Therefore, for example, in the case where it is desired to collectively display the URLs of pages containing similar information in a bookmark listing area, it is necessary for the user to perform an operation of reordering the bookmarks. More specifically, it is necessary to reorder the bookmarks so as to manage the URLs of the pages containing similar information as one group, or the like. This operation is excessively troublesome, when the number of the registered bookmarks is large.
On the other hand, it is possible to supply a browser which can be more easily utilized by ordinary people by introducing the technique of the three-dimensional information visualizer described earlier.